To: Professor Jolanta Janiszewska
From: Nick Kanel, Marcus Pereira, Matt Musso
Subject: AEV Lab 3
Date: February 17, 2016
Intro
In the Concept Screening and Scoring Lab, students began to use make charts with certain success criteria to compare the different designs. Each design was given either a “+”, “-”, or a “0” based on how it compared to the reference. This approach was a good way to educate the class on how to decide which design was best overall using net scores and weights, and also how to decide whether designs should be ended, developed, or combined.
The purpose of this lab is to get the teams to think about what designs to further improve and which ones to leave behind and not work on any more. There are some designs that are worth pursuing, but others have too many things wrong with them, which will just lead to more time spend on a design that would be better spent on improving an already-good design.
Discussion
Before running the AEV in class, a small adjustment was made. There was a realization that the battery on top was causing it to be slightly off balance and to pull in one direction. To resolve this issue, the battery was moved over one column on the board and it made it balance perfectly.
Once the first issue was settled, it was time to test the AEV on the track. While running the AEV on the track, an error was encountered. The AEV shot backwards before it went forwards, and that clearly wasn’t part of the plan. After double checking the coding of the Arduino, the reason was resolved. The order was accidentally mixed up and reversing the motors was in the beginning of the code. As for all other aspects when running it at the end of class, everything went smoothly.
Definitions:
CG Balance – Center of Gravity Balance (how level the AEV is).
Aerodynamics – How well the AEV can cut through the air
Maintenance – How easily the AEV can be modified
Weight – How much the AEV weighs
Cost – How much it will cost to build the AEV
There were four designs that the group was able to come up with. Each of the group members came up with one design, and then there was a final design that was a combination of all the best parts of each of the individual designs.
Design A was mostly good in that it had a good center of balance, which would allow it to glide along the track without leaning to one side, and it would also allow for the AEV to take a corner more smoothly. The aerodynamics of this design were on-par with the reference vehicle, which isn’t bad, but it could use a little bit of a redesign. This design is relatively low-maintenance, which means that it can be taken apart and worked on without having to take most of the vehicle apart. This is good because it allows for the team to make quick changes instead of taking twenty minutes to just flip one piece around. A negative to this design is the weight, but overall this design gets a +2 to the score and a 0.4 to the weighted score.
Design B seems to be far worse than any of the other designs mainly because it will require quite a bit of maintenance and also the center of gravity isn’t amazing. Because of this, it will take quite a bit of time to make any modifications and it also has the potential to slip off of the track when going around corners too quickly. Another downside to this design is that it weighs a lot. One pro here is that due to it having an outer shell, it will likely be more aerodynamic and less likely to be slowed down by speed. This design got a -0.65 for the weighted score.
Design C is, in theory, a very good design because it has good center of gravity and also good aerodynamics. The downsides to this design are that it will take a little bit more time to work on due to the presence of a wind shield and the fact that is weighs quite a bit more. Weight isn’t as big of a factor as maintenance, which means that it will have a higher score when weighted. This design got a 0.05 for the weighted score.
Design D is the design that was the combination of each of the individual designs. It is a very good design because it has good center of gravity and also good aerodynamics. The downsides to this design are that it will take a little bit more time to work on due to the presence of a wind shield and the fact that is weighs quite a bit more. Weight isn’t as big of a factor as maintenance, which means that it will have a higher score when weighted. This design got a 0.05 for the weighted score.
(Total and weighted scores for each AEV design)
The criterion chosen to evaluate the different AEV designs were based mainly on the functionality of the AEV, to include maintenance, weight, and balance. These were decided on because they are qualities that will make the most significant difference in the efficiency of the AEV. The design qualities were originally given a ‘+,’ ‘-,’ or ‘0’ value depending on whether the designs quality was better, worse, or the same as the reference vehicle.
The same was accomplished in more depth using the design scoring process in which weights were, instead, assigned to each criteria, which was then given a score based 1-5 and multiplied by the weight percent of that specific criteria. This evaluation thus gives a much more specific view of how designs compare to one another.
Conclusion
During the lab, knowledge was gathered concerning methods by which separate designs’ futures can be decided, that is whether they will be kept, thrown out, or improved upon. After some slight testing of Design A, the remaining designs were examined, and the process of elimination was undertaken. This resulted in the decision to develop designs C and D, and to drop design B. During testing of design A, it was discovered that the AEV was not balanced, but after two minor adjustments, the design was found to be very successful, and will likely serve as the primary platform off of which the final AEV design will be built.
| Success Criteria | Reference | Design A | Design B | Design C | Design D |
| CG Balance | 0 | + | – | + | + |
| Aerodynamics | 0 | 0 | + | + | + |
| Maintenance | 0 | + | – | – | – |
| Weight | 0 | – | – | – | – |
| Cost | 0 | 0 | 0 | 0 | 0 |
| Sum +’s | 0 | 2 | 1 | 2 | 2 |
| Sum 0’s | 5 | 2 | 1 | 1 | 1 |
| Sum –’s | 0 | 1 | 3 | 2 | 2 |
| Net Score | 0 | 1 | -2 | 0 | 0 |
| Continue ? | Combine | Yes | No | Develop | Develop |
Arduino Code
void myCode() {
//Accelerate
celerate(4,0,25,3);
//Go for 1 second
goFor(1);
//Set both mototrs to 20
setBoth(20);
//Go for 2 seconds
goFor(2);
//Reverse both
reverse(4);
//Set both to 25
setBoth(25);
//Go for 2 seconds
goFor(2);
//Stop both
brake(4);
} // DO NOT REMOVE. end of void myCode()
void setBoth(int speed) {
motorSpeed(1,speed);
motorSpeed(2,speed);
}